STRESS-STRAIN RELATIONSHIPDOE-HDBK-1017/1-93Properties of MetalsThe Shear Modulus of Elasticityis derived from the torsion of a cylindrical test piece.Its symbol is G.The Bulk Modulus of Elasticityis the elastic response to hydrostatic pressure andequilateral tension or the volumetric response to hydrostatic pressure and equilateraltension. It is also the property of a material that determines the elastic response to theapplication of stress.To determine the load-carrying ability and the amount of deformation before fracture, a sampleof material is commonly tested by a Tensile Test. This test consists of applying a graduallyincreasing force of tension at one end of a sample length of the material. The other end isanchored in a rigid support so that the sample is slowly pulled apart. The testing machine isequipped with a device to indicate, and possibly record, the magnitude of the force throughoutthe test. Simultaneous measurements are made of the increasing length of a selected portion atthe middle of the specimen, called the gage length. The measurements of both load andelongation are ordinarily discontinued shortly after plastic deformation begins; however, themaximum load reached is always recorded. Fracture point is the point where the materialfractures due to plastic deformation. After the specimen has been pulled apart and removed fromthe machine, the fractured ends are fitted together and measurements are made of the now-extended gage length and of the average diameter of the minimum cross section. The averagediameter of the minimum cross section is measured only if the specimen used is cylindrical.The tabulated results at the end of the test consist of the following. a.designation of the material under testb.original cross section dimensions of the specimen within the gage lengthc.original gage lengthd.a series of frequent readings identifying the load and the corresponding gagelength dimensione.final average diameter of the minimum cross sectionf.final gage lengthg.description of the appearance of the fracture surfaces (for example, cup-cone,wolf's ear, diagonal, start)MS-02Page 16Rev. 0
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